Some new designs of mobile communication devices—such as smart phones, tablet computers, and laptop computers—contain two or more Subscriber Identity Module (SIM) cards that provide users with access to multiple separate mobile telephony networks. Examples of mobile telephony networks include GSM, TD-SCDMA, CDMA2000, and WCDMA. Example multi-SIM mobile communication devices include mobile phones, laptop computers, smart phones, and other mobile communication devices that are enabled to connect to multiple mobile telephony networks. A mobile communication device that includes a plurality of SIMs and connects to two or more separate mobile telephony networks using two or more separate RF transceivers is termed a “multi-SIM-multi-active” or “MSMA” device. An example MSMA device is a “dual-SIM-dual-active” or “DSDA” communication device, which includes two SIM cards/subscriptions associated with two mobile telephony networks.
Because a multi-SIM-multi-active communication device has a plurality of separate radio frequency (“RF”) communication circuits or “RF chains,” each subscription on the MSMA communication device may use its associated RF chain to communicate with its mobile network at any time. However, because of the proximity of the antennas of the RF chains included in a MSMA communication device, the simultaneous use of the RF chains may cause one or more RF chains to desensitize or interfere with the ability of the other RF chains to receive RF signals.
Generally, receiver desensitization (referred to as “de-sense”), or degradation of receiver sensitivity, may result from noise interference of a nearby transmitter. For example, when two radios are close together with one transmitting on the uplink—the aggressor communication activity (“aggressor”)—and the other receiving on the downlink—the victim communication activity (“victim”)—signals from the aggressor's transmitter may be picked up by the victim's receiver or otherwise interfere with reception of a weaker signal (e.g., from a distant base station). As a result, the received signals may become corrupted and difficult or impossible for the victim to decode. Receiver de-sense presents a design and operational challenge for multi-radio devices, such as MSMA communication devices, due to the necessary proximity of transmitter and receiver.
Current MSMA communication devices implement a number of techniques to enable a victim subscription suffering from de-sense or poor reception performance to improve its reception performance on the device. For example, a MSMA communication devices may utilize a downlink closed-loop power control system to improve reception performance for a victim by prompting the victim to request that its mobile network increase output power, which increases the signal strength (and signal-to-interference ratio (SIR)) of the incoming signal. In another example, a MSMA communication devices may utilize channel quality indicator (CQI) reporting—a measure of the quality of one or more of the victim's communication channels—to improve reception performance quality for a victim by prompting the victim to report a low CQI index value, typically indicating a bad channel quality/reception performance quality. After receiving the victim's CQI report, the mobile network may adjust its output power accordingly, thereby increasing the SIR of the incoming signal that the victim receives.